SOMERVILLE, Mass. (AP) – A 21-year-old woman who allegedly stabbed a clothing store security guard with a hypodermic needle was held without bail Thursday after pleading not guilty to several charges including assault with a dangerous weapon.

Police said Jennifer Stacy of Cambridge stabbed the guard four times in the chest on Tuesday afternoon when he confronted her about shoplifting, then left the store and asked witnesses outside, “Does anyone else want AIDS?” Stacy then left in a car with two men, police said. She was arrested on Wednesday.

On Thursday in Somerville District Court, she pleaded not guilty to charges of shoplifting, armed robbery, assault and battery with a dangerous weapon, and assault and battery.

The 23-year-old Bob’s Stores guard, whose name was not released, was treated at a hospital and released. He was expected to undergo follow-up treatment.

The security guard was “nervous and very upset,” police spokesman Lt. Paul Upton said. “It’s a very emotional time for an individual who is dealing with an unknown crisis.”

Stacy also faces a warrant from Roxbury District Court, where she failed to appear in March on a shoplifting charge, police said.